Nitride semiconductor device

Abstract

A nitride semiconductor device includes a substrate; a nitride semiconductor layered structure disposed on the substrate and having a channel region; a first electrode and a second electrode both disposed on the nitride semiconductor layered structure; a first p-type nitride semiconductor layer disposed between the first electrode and the second electrode; and a first gate electrode disposed on the first p-type nitride semiconductor layer. The nitride semiconductor layered structure includes a first recess. The first p-type nitride semiconductor layer is at least partially disposed inside the first recess, and is separated from a side surface of the first recess.

What is claimed is: 
     
       1. A nitride semiconductor device, comprising:
 a substrate; 
 a nitride semiconductor layered structure disposed on the substrate and having a channel region; 
 a first electrode and a second electrode both disposed on the nitride semiconductor layered structure; 
 a first p-type nitride semiconductor layer disposed between the first electrode and the second electrode; and 
 a first gate electrode disposed on the first p-type nitride semiconductor layer, 
 wherein the nitride semiconductor layered structure includes a first recess, and 
 the first p-type nitride semiconductor layer is at least partially disposed inside the first recess, and is separated from a side surface of the first recess. 
 
     
     
       2. The nitride semiconductor device according to  claim 1 , wherein
 the nitride semiconductor layered structure includes:
 a first nitride semiconductor layer; and 
 a second nitride semiconductor layer disposed on the first nitride semiconductor layer and having a band gap that is greater than a band gap of the first nitride semiconductor layer, and 
 
 a bottom surface and the side surface of the first recess are a surface of the second nitride semiconductor layer. 
 
     
     
       3. The nitride semiconductor device according to  claim 1 , wherein
 the nitride semiconductor layered structure includes:
 a first nitride semiconductor layer; 
 a second nitride semiconductor layer disposed on the first nitride semiconductor layer and having a band gap that is greater than a band gap of the first nitride semiconductor layer; and 
 a third nitride semiconductor layer partially disposed on the second nitride semiconductor layer and having a band gap that is greater than the band gap of the first nitride semiconductor layer, 
 
 a bottom surface of the first recess is a surface of the second nitride semiconductor layer, and 
 the side surface of the first recess is a surface of the third nitride semiconductor layer. 
 
     
     
       4. The nitride semiconductor device according to  claim 1 , wherein
 the nitride semiconductor layered structure includes:
 a first nitride semiconductor layer; 
 a second nitride semiconductor layer partially disposed on the first nitride semiconductor layer and having a band gap that is greater than a band gap of the first nitride semiconductor layer; and 
 a third nitride semiconductor layer disposed on the first nitride semiconductor layer and the second nitride semiconductor layer and having a band gap that is greater than the band gap of the first nitride semiconductor layer, and 
 
 a bottom surface and the side surface of the first recess are a surface of the third nitride semiconductor layer. 
 
     
     
       5. The nitride semiconductor device according to  claim 1 , wherein
 the nitride semiconductor layered structure includes:
 a first nitride semiconductor layer; 
 a second nitride semiconductor layer disposed on the first nitride semiconductor layer and having a band gap that is greater than a band gap of the first nitride semiconductor layer; and 
 a third nitride semiconductor layer disposed on the first nitride semiconductor layer and the second nitride semiconductor layer and having a band gap that is greater than the band gap of the first nitride semiconductor layer, 
 
 the bottom surface of the first recess is a surface of the third nitride semiconductor layer, and 
 the side surface of the first recess is a surface of the second nitride semiconductor layer and a surface of the third nitride semiconductor layer. 
 
     
     
       6. The nitride semiconductor device according to  claim 1 , further comprising:
 a second p-type nitride semiconductor layer disposed between the first p-type nitride semiconductor layer and the second electrode; and 
 a second gate electrode disposed on the second p-type nitride semiconductor layer, 
 wherein the nitride semiconductor layered structure includes a third recess, and 
 the second p-type nitride semiconductor layer is disposed inside the third recess and is separated from a side surface of the third recess. 
 
     
     
       7. The nitride semiconductor device according to  claim 1 , wherein
 the side surface of the first recess is rounded. 
 
     
     
       8. The nitride semiconductor device according to  claim 1 , wherein
 the first gate electrode is in Schottky contact with the first p-type nitride semiconductor layer, and 
 a first parasitic capacitance between the first gate electrode and the first p-type nitride semiconductor layer is greater than a second parasitic capacitance between the first p-type nitride semiconductor layer and the channel region. 
 
     
     
       9. The nitride semiconductor device according to  claim 1 , wherein
 a hole concentration of the first p-type nitride semiconductor layer decreases one of continuously and stepwise from a top surface toward a bottom surface of the first p-type nitride semiconductor layer, the top surface being adjacent the first gate electrode and the bottom surface being adjacent the nitride semiconductor layered structure. 
 
     
     
       10. The nitride semiconductor device according to  claim 1 , wherein
 in a plan view, the first p-type nitride semiconductor layer is disposed inside the first recess in entirety, 
 the side surface of the first recess includes a first side surface closer to the first electrode than the second electrode and a second side surface closer to the second electrode than the first electrode, and 
 the first p-type nitride semiconductor layer is separated from the first side surface and the second side surface. 
 
     
     
       11. The nitride semiconductor device according to  claim 1 , wherein
 the side surface of the first recess includes a first side surface closer to the first electrode than the second electrode and a second side surface closer to the second electrode than the first electrode, and 
 the first p-type nitride semiconductor layer covers the first side surface and is separated from the second side surface. 
 
     
     
       12. The nitride semiconductor device according to  claim 2 , wherein
 the first nitride semiconductor layer includes GaN, and 
 the second nitride semiconductor layer includes AlGaN. 
 
     
     
       13. The nitride semiconductor device according to  claim 3 , wherein
 the nitride semiconductor layered structure includes a fourth recess, 
 the first electrode is at least partially disposed inside the fourth recess, and 
 a bottom surface and a side surface of the fourth recess are a surface of the third nitride semiconductor layer. 
 
     
     
       14. The nitride semiconductor device according to  claim 3 , wherein
 the third nitride semiconductor layer includes AlGaN and has a composition ratio different from a compositional ratio of the second nitride semiconductor layer. 
 
     
     
       15. The nitride semiconductor device according to  claim 4 , wherein
 the nitride semiconductor layered structure includes a second recess penetrating through the second nitride semiconductor layer, 
 the second recess is disposed below the first recess, and 
 a bottom surface and a side surface of the second recess are a surface of the second nitride semiconductor layer. 
 
     
     
       16. The nitride semiconductor device according to  claim 4 , wherein
 the nitride semiconductor layered structure includes a second recess in the second nitride semiconductor layer, 
 the second recess is disposed below the first recess, 
 a bottom surface of the second recess is a surface of the first nitride semiconductor layer, and 
 a side surface of the second recess includes a surface of the second nitride semiconductor layer. 
 
     
     
       17. The nitride semiconductor device according to  claim 14 , wherein
 the band gap of the second nitride semiconductor layer is greater than the band gap of the third nitride semiconductor layer.